I need to detect and count a number of metal plates coming by my sensor. I need to do it cheap as possible. There are around 1-2 centimeters between the plates, and they are 3 centimers thick. The sensor can get pretty close to the plates: ~1cm.
What do you see as my options?
I have tried an IR distance sensor, which works OK. Problem is that the plates are black, so I need to use a lot of power in my emitter LED to light up the black. Besides day light and other light sources might interfere.
I've looked into inductive proximity sensors, but I haven't found any IC's are reference designs for this. The ones that you can buy for automation are to expensive.
Any other ideas? :)
To clarify. Actually it is a stack of weight plates that is moved up and down (like in a gym machine):
I need to count how many plates passed a curtain point. I was thinking if it is possible to do something electromagnetic? Create a long coil (the blue line in the drawing) or something similar?